DynamicLoader.swift

//
//  DynamicLoader.swift
//  PerfectLib
//
//  Created by Kyle Jessup on 7/13/15.
//	Copyright (C) 2015 PerfectlySoft, Inc.
//
//	This program is free software: you can redistribute it and/or modify
//	it under the terms of the GNU Affero General Public License as
//	published by the Free Software Foundation, either version 3 of the
//	License, or (at your option) any later version, as supplemented by the
//	Perfect Additional Terms.
//
//	This program is distributed in the hope that it will be useful,
//	but WITHOUT ANY WARRANTY; without even the implied warranty of
//	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//	GNU Affero General Public License, as supplemented by the
//	Perfect Additional Terms, for more details.
//
//	You should have received a copy of the GNU Affero General Public License
//	and the Perfect Additional Terms that immediately follow the terms and
//	conditions of the GNU Affero General Public License along with this
//	program. If not, see <http://www.perfect.org/AGPL_3_0_With_Perfect_Additional_Terms.txt>.
//

#if os(Linux)
import SwiftGlibc
#else
import Darwin
#endif

class DynamicLoader {
	
	// sketchy! PerfectServerModuleInit is not defined as convention(c)
	// but it does not seem to matter provided it is Void->Void
	// I am unsure on how to convert a void* to a legit Swift ()->() func
	typealias InitFunction = @convention(c) ()->()
	
	let initFuncName = "PerfectServerModuleInit"
	
	init() {
		
	}
	
	func loadFramework(atPath: String) -> Bool {
		let resolvedPath = atPath.stringByResolvingSymlinksInPath
		let moduleName = resolvedPath.lastPathComponent.stringByDeletingPathExtension
		let file = File(resolvedPath + "/" + moduleName)
		if file.exists() {
			let realPath = file.realPath()
			return self.loadRealPath(realPath, moduleName: moduleName)
		}
		return false
	}
	
	func loadLibrary(atPath: String) -> Bool {
		let resolvedPath = atPath.stringByResolvingSymlinksInPath
		let moduleName = resolvedPath.lastPathComponent.stringByDeletingPathExtension
		let file = File(resolvedPath)
		if file.exists() {
			let realPath = file.realPath()
			return self.loadRealPath(realPath, moduleName: moduleName)
		}
		return false
	}
	
	private func loadRealPath(realPath: String, moduleName: String) -> Bool {
		let openRes = dlopen(realPath, RTLD_NOW|RTLD_LOCAL)
		if openRes != nil {
			// this is fragile
			let newModuleName = moduleName.stringByReplacingString("-", withString: "_").stringByReplacingString(" ", withString: "_")
			let symbolName = "_TF\(newModuleName.utf8.count)\(newModuleName)\(initFuncName.utf8.count)\(initFuncName)FT_T_"
			let sym = dlsym(openRes, symbolName)
			if sym != nil {
				let f: InitFunction = unsafeBitCast(sym, InitFunction.self)
				f()
				return true
			} else {
				print("Error loading \(realPath). Symbol \(symbolName) not found.")
				dlclose(openRes)
			}
		} else {
			print("Errno \(String.fromCString(dlerror())!)")
		}
		return false
	}
	
}